The multicellular eucaryotic Volvox will be characterized with respect to its potential value as a model system for the study of the aging process. This organism appears to possess both the simplicity and ease of laboratory manipulation characteristics of unicellular microorganisms and yet is also capable of undergoing true aging and senescence; processes generally associated with only more complex multicellular organisms. The role of mitochondria in the aging process in Volvox will also be examined in considerable detail. According to a widely accepted theory of aging, lipid peroxidation is though to represent an important mechanism of cell deterioration. Since mitochondria are believed to be primary targets of lipid peroxidation, a structural and functional examination of this organelle during the Volvox life cycle should aid in the further evaluation of this theory.